This invention relates to robotics, and in particular, it relates to a method and apparatus for calibrating a robot.
The very essence of a robotic apparatus is that its movements are accurately predetermined so as to accurately carry out an intended operation such as handling or working on an object, the latter including, for example, welding or inspecting an object.
To further improve upon the accuracy of a robot's predetermined movements, there is described in my copending applications Ser. No. 262,492, filed May 4, 1981, now U.S. Pat. No. 4,453,085 and Ser. No. 348,803, filed Feb. 16, 1982, systems for guiding the robots through the course of their intended movements, to further enhance the accuracy of such movements.
However, no matter how perfect the original predetermined movements or no matter how accurate the guidance systems for enhancing the robot's movements, the nature of the environment in which the robots are utilized, including environmental conditions exterior to the robot make it virtually impossible to assure perfect positional accuracy at all times.
For example, many robots, particularly multi-joint articulated robots, are generally not capable of maintaining their positional actions over a long period of time. Furthermore when approaching a given desired position from different paths, they often provide different results, even when functioning as a result of the same computer input commands. This can be extremely difficult in a fully flexible automatic factory situation where different path commands may have to be generated by the computer and the robot is expected to follow them under all conditions.
In addition to my co-pending applications which relate to further enhancing the accuracy of the predetermined robot movements, another apparatus quite suitable for this purpose is shown in the Pinkney et al U.S. Pat. No. 4,219,847.
Hence, notwithstanding the improved means discussed above and known heretofore for enhancing guiding of the robot arm, there still exists a need to correct inaccuracies in the robot's position which cannot be corrected using known predetermined and improved guidance means.